There’s long been a debate over the impact of genetic modification on crop yields. While agricultural biotechnology’s proponents argue that genetically modified crops demonstrate higher yields, its critics contend that organic production and conventional crop breeding result in higher yields than genetic modification. The problem is that both sides are able to marshal data in support of their position by cutting the data in particular ways. Under ideal growing conditions or when pest infestation levels are high, genetically modified crops often demonstrate higher yields. But under less-than-ideal growing conditions or when pest infestation levels are lower, conventional (non-GM) varieties perform better. When measured in terms of monoculture yield (output per acre of a single crop variety), GM varieties tend to have higher productivity. When measured in other ways (total caloric output per acre, cost per calorie, etc.), conventional varieties tend to have higher productivity. It often comes down to how you define and measure productivity.
A new study, titled “Sustainability and innovation in staple crop production in the US Midwest” and published in the International Journal of Agricultural Sustainability is weighing in on the debate using an interesting methodology. The study seeks to evaluate the relative impact of genetic modification and selective crop breeding to evaluate the importance of each in improving crop yields. It does this by comparing maize, rapeseed, soybean, and canola output in Canada and the United States (which have embraced both genetic modification and selective breeding) and Western Europe (which has generally rejected genetic modification but has embraced selective breeding).
The four crops selected are the most widely cultivated GM crops in the world. The study’s authors note that while GM varieties of these crops are virtually absent in Europe, in Canada and the United States cultivation of GM varieties has reached near saturation levels, with an estimated 95% of rapespeed, 94% of soy and cotton, and 88% of maize, grown in the United States being a genetically modified variety. Based on their comparison, the study’s authors conclude that,
These results suggest that yield benefits (or limitations) over time are due to breeding and not GM, as reported by others, because W. Europe has benefitted from the same, or marginally greater, yield increases without GM. Furthermore, the difference between the estimated yield potential and actual yield or ‘yield-gap’ appears to be uniformly smaller in W. Europe than in the US Midwest. Biotechnology choices in the form of breeding stock and/or management techniques used in Europe are as effective at maintaining yield as are germplasm/management combinations in the United States.
The study recommends several strategies for improving yields and reducing potential vulnerability to exogenous shocks resulting from weather, disease and pests. These recommendations generally center on expanding crop diversity which has sharply declined over the past forty years. The article is written in an accessible format even to the lay reader and is definitely worth a read.
Posted by http://globalfoodpolitics.wordpress.com/2013/07/05/improving-crop-yields/ on July 5, 2013